I'm playing around with ZFS. Currently, I just use it for storage, with a zpool of 4 sata disks. The system and boot disk is still formatted with UFS. As I'm quite pleased with ZFS features, I'd like to try ZFS on root. The ZFS wiki is quite clear on how to proceed : if the boot and root are on the same disk, you'll have to use bsd labels. The thing is, I read somewhere that ZFS doesn't enable write caching on drives if not used on whole disks. 1. Is it still true on freebsd or just for opensolaris. 2. As the only other(s) label(s) on disk would be the (readonly) boot and swap label, I don't think write caching would be a problem. So how can I tell ZFS it's ok to enable it on the disk (or enable it manualy if necessary and of any use). 3. I'd like to keep the storage pool (zraid1) separated from the system pool (just one disk). The wiki states that we may encounter problems with more than one pool in use : is it still the case ? I know the whole ZFS thing is still experimental, but with it's overall performance, it would really be a shame not to give it its chance. Thanks for your comments. Arnaud Houdelette
I don't have a definite answer to your first two questions (I've got a similar set up and would be interested to get some definite answers to those) however I'd like to comment on your third point... On May 21, 11:00 pm, arnaud.houdele...@tzim.net (Arnaud Houdelette) wrote:> 3. I'd like to keep the storage pool (zraid1) separated from the system > pool (just one disk). The wiki states that we may encounter problems > with more than one pool in use : is it still the case ?as for encountering problems with multiple zpools, my impression from the mailing lists is that it seems to work fine for some people and not for others... (i'm in the latter category, unfortunately) but what struck me as odd is the desire to create two separate zpools - one for data storage and one for the system. i think one of zfs's greatest strengths is the abstraction/separation between disks and filesystems. unless you're planning on removing/recreating the raidz1 pool in the near future, it seems a bit odd to put your system on a single/separate, non-redundant drive when you could just create a raidz across all four disks with storage and system filesystems in the one raidz pool. this way you don't lose anything if the disk you chose to run the OS from happens to fail, or even just gets a bad sector in an unfortunately crucial location... And even if you were going to recreate the raidz pool in the near future, it shouldn't be too hard to backup the system filesystems with zfs snapshot/send/receive commands, recreate the pool and then restore the system filesystems from the backup Andrew
Pawel Jakub Dawidek a ?crit :> On Wed, May 21, 2008 at 03:00:41PM +0200, Arnaud Houdelette wrote: > >> I'm playing around with ZFS. >> >> Currently, I just use it for storage, with a zpool of 4 sata disks. >> The system and boot disk is still formatted with UFS. >> >> As I'm quite pleased with ZFS features, I'd like to try ZFS on root. The >> ZFS wiki is quite clear on how to proceed : if the boot and root are on >> the same disk, you'll have to use bsd labels. >> >> The thing is, I read somewhere that ZFS doesn't enable write caching on >> drives if not used on whole disks. >> > > This is only the case for Solaris, as it turns off write cache by > default. In FreeBSD we always turn on write cache, so don't worry, it > will just work on FreeBSD. >Thanks for the info.> [...] > >> 3. I'd like to keep the storage pool (zraid1) separated from the system >> pool (just one disk). The wiki states that we may encounter problems >> with more than one pool in use : is it still the case ? >> > > AFAIK it was never the case. Where did you find that information > exactly? I've two systems that have more than one pool configured and > never had any problems. >It's clearly stated in the ZFS page of the FreeBSD Wiki : http://wiki.freebsd.org/ZFSKnownProblems , 3rd entry states : Kernel panic and/or data loss may result when more than one ZPOOL is active / in use. Symptoms: various, including (unverified) possibility of data loss. References: http://lists.freebsd.org/pipermail/freebsd-fs/2008-February/004377.html I'll try for myself then. Arnaud Houdelette
On Wed, May 21, 2008 at 03:00:41PM +0200, Arnaud Houdelette wrote:> I'm playing around with ZFS. > > Currently, I just use it for storage, with a zpool of 4 sata disks. > The system and boot disk is still formatted with UFS. > > As I'm quite pleased with ZFS features, I'd like to try ZFS on root. The > ZFS wiki is quite clear on how to proceed : if the boot and root are on > the same disk, you'll have to use bsd labels. > > The thing is, I read somewhere that ZFS doesn't enable write caching on > drives if not used on whole disks.This is only the case for Solaris, as it turns off write cache by default. In FreeBSD we always turn on write cache, so don't worry, it will just work on FreeBSD. [...]> 3. I'd like to keep the storage pool (zraid1) separated from the system > pool (just one disk). The wiki states that we may encounter problems > with more than one pool in use : is it still the case ?AFAIK it was never the case. Where did you find that information exactly? I've two systems that have more than one pool configured and never had any problems. -- Pawel Jakub Dawidek http://www.wheel.pl pjd@FreeBSD.org http://www.FreeBSD.org FreeBSD committer Am I Evil? Yes, I Am! -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 187 bytes Desc: not available Url : http://lists.freebsd.org/pipermail/freebsd-stable/attachments/20080529/28df3525/attachment.pgp